1. n. [Well Workover and Intervention]

A type of tool-string centralizer, generally used in through-tubing applications, that employs hydraulic force to energize the centralizer arms or bows. Through-tubing operations sometimes require the tool string to be centralized within the casing or liner below the tubing. The relatively large expansion required for this is not generally within the operating range of conventional centralizer models.

See: tool string